This invention relates to the synthesis of hafnium chloride alkoxides which can be used for the hafnium metal oxide thin film deposition via chemical vapor deposition (CVD) or atomic layer chemical vapor deposition (ALCVD) process.
Currently, zirconium and hafnium precursors used for CVD or ALCVD are HfCl4, Hf(OR)4, where R=alkyl, such as CH(CH3)2, Hf(tmhd)4, where tmhd=2,2,6,6-tetramethyl-3,5-heptanedionato, Hf(tfac)4, where tfac=trifluoroacetylacetonate, and Hf(NO3)4, and similar precursors with zirconium components. For metal gate oxide applications, HfCl4 has been reported as a potential source for a pure HfO2 thin film deposition. Ryan C. Smith et al. Chemical Vapor Deposition of the Oxides of Titanium, Zirconium and Hafnium for Use as High-k Materials in Microelectronic Devices. A Carbon-free Precursor for the Synthesis of Hafnium Dioxide, Advanced Materials for Optics and Electronics 10, 105-114, 111-113 (2000).
As for the other precursors, Hf(OR)4 is extremely air and moisture sensitive and is difficult to handle; Hf(tmhd)4 is stable, but induces carbon contamination, which is difficult to remove; Hf(tfac)4 is a volatile precursor, but its use includes a risk of fluorine contamination. There is no report about application of Hf(NO3)4 in ALCVD.
Because hafnium and zirconium have nearly identical electron configurations, they have nearly identical chemical properties. Thus, as is well know to those of ordinary skill in the art, they are virtually interchangeable in chemical compounds, and exhibit similar characteristics when used in semiconductor devices.
A method of making a precursor for a thin film formed by chemical vapor deposition processes, includes mixing ZCl4 with H(tmhd)3 solvent and benzene to form a solution, where Z is an element taken from the group of elements consisting of hafnium and zirconium; refluxing the solution for twelve hours in an argon atmosphere; removing the solvents via vacuum, thereby producing a solid compound; and sublimating the compound at 200xc2x0 C. in a near vacuum of 0.1 mmHg.
A ZOx precursor, for use in a chemical vapor deposition process, includes a Z-containing compound taken from the group of compounds consisting of ZCl(tmhd)3 and ZCl2(tmhd)2.
It is an object of the invention to provide hafnium precursors which may be used for the hafnium metal oxide thin film deposition via CVD or ALCVD process.
A further object of the invention is to reduce chlorine contamination while still providing a sufficiently volatile precursor.
Another object of the invention is to use alkoxide ligands to partially replace the chlorine, resulting in hafnium dichloride dialkoxide or hafnium chloride trialkoxide.